Trailer steering mechanism



April 8, 1952 o. J. SEI-:LY 2,592,475

TRAILER STEERING MECHANISM Filed April 5. 1949 7 sheets-sheet 1 y BY rro/Qwf ,15

April 8, 1952 o. J. sl-:l-:LY 2,592,475

' TRAILER STEERING MECHANISM Filed April 5. 1949 7 Sheets-Sheet 2 Orry :7A/vifs 5ft-L Y, IN VEN TOR.

rroR/VEVS.

April 8, 1952 o. J. sEELY 2,592,475

TRAILER STEERING MECHANIYSM Filed April 5. 1949 7 Sheets-Sheet 5 April 8, 1952 o. J. sEELY TRAILER STEERING MECHANISM 7 Sheets-Sheet 4 Filed April 5. 1949 rrsf fik/M55 55212 .INVENTOR.

April 8, 1952 Q. .1. sEELY 2,592,475

TRAILER STEERING MECHANISM Filed April 5. 1949' 7 Sheets-Sheet 6 u l W Orry r/Iq/vfs ,55a s:

INVEN TOR.

BY Wam/f rroR/vffs jatented Apr. 8,' 1 ,952

TRAILER STEERING MECHANISM Otty James Secly, Oildale, Calif., assignorJ of thirty per cent to R. N. Lancaster, Bakersfield,

Calif.

Application April 5, 1949, Serial No. 85,507

22 Claims. (Cl. 2480-3355) This invention relates to an apparatus applicable to a towed vehicle having turnable wheels and a towing vehicle for the purposes of guiding the turnable wheels of the towed vehicle in accordance with the direction of turn of the towing vehicle and direction of movement backward or forward of the vehicles.

The main object of the present invention is to provide an apparatus applicable to a towed vehicle having turnable wheels and a towing vehicle having turnable wheels which apparatus is actuatable when the vehicles are moving forward and backward and the turnable wheels of the towing vehicle arey turned to turn the turnable wheels of the towed vehicle in a direction opposite the direction of turn of the turnable wheels of the towing vehicle.

Another object of the present invention is to provide an apparatus applicable to a towed vehicle having turnable wheels and a towing vehicle wherein the apparatus includes means oscillatably mounted on the towed vehicle and connected with the turnable wheels of the towed vehicle so as to turn the turnable wheels when tilted, means connecting the towing vehicle and the oscillatable means and responsive to misalignment of the vehicles for tilting the oscillatable means to turn the turnable wheels and which apparatus includes means for reversing the direction of tilt of the oscillatable means depending on whether the vehicles are moving forward or backward.

Another object of the present invention is to provide an apparatus as described in the above paragraph in which booster means are provided for assisting the turning of the turnable wheels of the towed vehicle.

Another object is to .provde a towed vehicle having turnable wheels and a towing vehicle equipped with apparatus as set out in the above paragraphs for turning the turnable wheels of the towed vehicle.

Another object of the present invention is to provide a towed vehicle having turnable wheels and a towing vehicle having turnable wheels, the vehicles being equipped with apparatus actuatable for turning the turnable wheels of the towed vehicle so that they track the turnable wheels of the towing vehicle.

With the foregoing and other objects in view, which will be made manifest in the following detailed description and specifically pointed out in the appended claims, reference is had to the accompanying drawings for an illustrative embodiment of the invention, wherein:

. Figure 1 discloses a plan View of the towed 2 Y vehicle and the towing vehicle equipped with'thev apparatus in which the vehicles are moving "forward and to the right;

Fig. 2 is a plan View showing the vehicles moving forward and to the left;

Fig. 3 is a plan view of the vehicles moving .backward and to the left;

Fig. 4 is a plan view showing the vehicles moving backwardly to the right;

Fig. 5 is an enlarged lJlan view in section through the part of the apparatus located between the towed vehicle and the towing vehicle;

Fig. 6 is a sectional view along lines 6-6 of Fig. 5;

Fig. 7 is a sectional view along lines 1-1 of Fig. 6 with parts broken away; 3

Fig. 8 is a sectional View along lines 3--8 of Fig.

Fig. 9 is a plan view with parts broken away showing the tilt bar and the lead screw and valves controlled by the screw;

Fig. 10 is a sectional vew along lines Illl0 of Fig. 9;

Fig. l1 is a view along lines H-II of Fig. 9;

Fig. 12 is a diagrammatic view showing the positions of the valves controlled by the lead screw; and

Fig. 13 is another view showing the valves in another position. I Y

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, Fig. 1 shows a towing vehicle generally indicated at l5 and towed vehicle gen' erally indicated at I6, the two vehicles being connected to one another by means of a hitchV I1 of any suitable means. The towed vehicle i5 has a motor I9, a manifold 20, a transmission 2| with the gear shift 22 leading thereinto and there is the usual drive from the transmission to rear wheels 23. Although only two rear wheels are shown, it is obvious that more rear wheels could be provided on the towing vehicle without departing from the scope of the invention. The towing vehicle also has turnable wheels 25 so as to permit the towing vehicle to be steered.v

The towed vehicle is equipped with turnable wheels 21 which are mounted for4 turning 'movement on the towed vehicle and, although only'two turnable wheels are shown, the towed vehicle could be equipped with other wheels which would not be turnable and if other wheels were provided the rear wheels of the towed vehicle would be the turnable wheels.

The apparatus for turning the turnable wheels of the towed vehicle includes a control housing 3,0

which is pivotally mounted at 3| to the towing vehicle, said housing having a piston 33 slidable therewithin, the piston being equipped with a piston rod 34 which is pivoted to a main tilt lever 36, said main tilt lever being pivoted on the towed vehicle at 31. The piston 33 is approximately centered within the control housing 30 by means of compression springs 39 and 40 so that whenever thevehicles are misaligned the control housing or cylinder will move relative to the piston 33, or vice versa, depending upon the way the vehicles are considered, and therefore the springs 39 and 40 are compressed thereby applying force to the main tilt lever 35 to pivot the lever.

The main tilt lever 36 is connected by a lever 42 to stub shaft 58 on a nut 51 which is movable along a lead screw 55 that is rotatably mounted on the tilt bar 43. The tilt bar 43 is pivotally suspended by means of a frame 45 that is pivotally mounted at 46 on the chassis of the towed vehicle. The frame 45 isrigid with the tilt bar 43 so that the tilt bar 43 and frame 45 swing in unison about the pivot bolt 46 which is located above but intermediate the ends of the tilt bar 43.

The frame 45 includes a push lever 41 which is rigidly connected to the tilt bar and pivoted to a push rod 49, said push rod 49 being pivotally connected to the steering apparatus 50 for the rear wheels. Therefore, when the lever 42 is located as it is shown in Fig. 1 and the vehicles are misaligned, the main tilt lever 36 will tilt the tilt b ar 43 thereby swinging the push lever 41, thereby pushing the push rod 49 and turning the turnable wheels 21 of the towed vehicle. In Fig. 1, the vehicles are shown moving forward and the towing vehicle is turning to the right and therefore the position of the parts shown in Fig. l is such that the turnable wheels 21 of the towed vehicle turn in the direction opposite to the direction of turn of the turnable wheels 25 of the towing vehicle, this resulting in the turnable wheels 21 tracking the turnable wheels 25 so that the towed vehicle effectively follows the towing vehicle, which is desired. However, if the vehicles are moving backward it is desired that the turnable wheels 25 and 21 be turned in the same direction as shown in Fig. 1, which is so as can be seen in Fig. 4 wherein the vehicles are shown moving backward and to the right. However, in this case the vehicles are misaligned in the opposite direction from that when the vehicles are moving forward and thereforesome means must be provided to reverse a part of the apparatus so that the turnable wheels 21 will be turned in the right direction.

This reversing apparatus comprises a motor 53, which is preferably an electric motor, which motor is connected by means of a double uni-` versal joint 54 to a lead screw 55, said lead screw being rotatably mounted within tilt bar 43. The lever 42 is pivoted on a control nut 51 which is best seen in Fig. 10, which control nut rides on lead screw 55, said control nut having an upwardly extending stub shaft 58 on which lever 42 is pivoted, and a downwardly extending stub shaft 59 for purposes to be described. Motor 53 is of the reversing type so that when energized through one set of leads the motor rotates in one direction, and when energized through another set of leads the motor rotates in the opposite direction, this arrangement being so common that no detailed description is thought necessary. This reversing control motor 53, when actuated in the proper manner, runs the control nut 51 from one end of lead screw 55 to the other end of lead screw 55, thereby reversing the di- 4 rection in which the tilt bar 43 is tilted when moved by lever 42.

With this reversing construction it will be seen by comparing Figs. 1, 2, 3 and 4, that whatever direction the turnable wheels 25 on the towing vehicle are turned when the towing vehicle is moving, the turnable wheels 21 of the towed vehicle will be turned in the opposite direction which will be the correct direction whether the vehicles are moving forward or backward. For instance, by comparing Figs. 2 and 3 it can be seen that the turnable wheels 25 and 21 are turned in the same direction although in Fig. 2 the vehicles are moving forward and in Fig. 3 the vehicles are moving backward. The difference between backward and forward movement of the vehicles is that the vehicles are misaligned in the opposite direction and since the reversing mechanism is adapted to reverse the direction of tilt of the tilt bar 43, the opposite effects of the control housing 30, the piston 33, springs 39 and 40 are taken into account.

In order that the reversing motor 53 will correctly reverse the direction of tilt of the tilt bar 43 when the vehicles change direction from for.- ward to backward, or from backward to forward, a control system including wiring leading from contacts 60 and 6I mounted near the gear shaft 22 to the motor 53 is provided. Means are also provided for stopping movement of the control nut 51 as it reaches the end of the tilt bar 43 and these means comprise switches 63 and 64 which have pivotally mounted levers 65 resting against spring-constrained detentsv 56 which controls the contacts of switches 63 and G4. When the lower switch 64 is in the position shown in Fig. 9, the circuit through switch 64 is closed so that the motor 53 can be energized through leads 61 and 68 and the motor 53 will remain energized until the control nut 51 moves down, as the device is depicted in Fig. 9, contacts lever 65 of switch 64, and opens the contacts of switch 64. thereby opening the circuit and stopping the motor 53.

Switch 63, as shown in Fig. 9, is in open circuit position so that motor 53 cannot be energized through leads 13 and 1 I.

Contacts E0 near transmission 2| and gear shift 22 may be termed the rear direction contacts, and contacts 6I the forward direction contacts because when the gear shift 22 is shifted to the left, as the apparatus is depicted in Fig. 1, contacts 50 will be closed and a circuit completed, as best shown in Fig. 4, through leads 61 and 68 through terminal box 14 and motor 53, back through lead 15 to a battery 1G on the towing vehicle I5. If the gear shift 22 is moved to the right as the parts are depicted in Fig. 1, contacts Si will be closed, thereby closing a circuit through lead 1i) to switch 63 through lead 1l to terminal box 14 on the towed vehicle to motor 53 from the motor back to the terminal box and through lead 15 to the battery 1G on the towing vehicle l5.

Booster means are provided for assisting the turning of turnable wheels 21 of the towed vehicle l5 and although a system is to be described which works off the intake manifold of the towing vehicle, the system is not to be limited to a vacuum actuated system but may be a pressure actuated system, or actuated hydraulically or electrically, and the invention is not intended to be limited by the showing of a vacuum-operated system. The booster means include pivotally mounted cylinders and 87| which cylinders are pivotally mounted at 82 and 83 on the towed vehicle |6. Cylinder 89 is equipped with a piston and piston rod 85 and cylinder 9| is equipped with a piston and piston rod 86, piston rods 85 and 86 being pivoted on tilt bar 43 as shown in Fig. 1 and shown in more detail in Figs. 9 and 10, tilt bar 43 having upwardly extending knobs receivable within sockets provided on piston rods 85 and 86. Conduits which will be described in detail are provided to connect the intake manifold 29 to the cylinders 89 and 8|, the conduits being connected to several control valve means before they reach the cylinders 89 and 9| so that either cylinder 89 or cylinder 8| is connected to the source of vacuum, that is, the intake manifold, depending upon the direction of turn of the towing vehicle and, also, depending upon whether the vehicles are moving forward or backward.

There are two pairs of stations or valves, 99 and 9| being the first pair, and 92 and 93 being the second pair, and these valves may be also termed control stations since if one of the valves is connected to a source of vacuum and the valve is open, then the booster cylinder 89 or 8| to which it is connected will be connected to a source of vacuum and therefore actuated. yThe pairs of valves are not connected directly to the source of vacuum, that is, the manifold 29, but are connected to two main control Valves 95 and 96 vwhich are mounted on the control housing 39 as can best be seen in Fig. l. Briefly, then, the supply vacuum is connected first to the main control Valves 95 and 99 which are in turn connected to the control stations or valves 99, 9|, 92 and 93 which, in turn, are connected to the booster cylinders 89 and 8|. Stations or valves 99, 9|, 92 and 93 are connected to cylinders 89 and 8| by means of conduits 99a, 9|a, 92a and 93a, see Figs. l, 2, 3 and 4, valves or stations 99 and 92 being connected to cylinder 89 and valves or stations 9| and 93 being connected to cylinder 8 l The plugs for valves 99, 9|, 92 and 93 are moved from open to closed position, and vice versa, by means of arms 98 which arms are positioned one above the other, as shown in Fig. 19, and slidable through an oscillatable support |99, said support `being oscillatably mounted on downwardly extending stub shaft 59 of control nut 51, see Fig. 10. The arms 98 are therefore controlled by the movement of control nut 51 and therefore open and closed, depending on whether the control nut is at one end or the other end of tilt bar 43. The control valves 99, 9|, 92 and 93 are supported from frame 45, as can best be seen in dot-dash lines in Fig. 19, by means of a plate |9|, see Figs. 9 and 10.

The pairs of valves 99 and 9|, and 92 and 93, are so initially set up and connected by arms 98 to oscillatable support |99 so that one valve of each pair is open and the other valve of each pair is closed when the control nut 51 is at one end of the tilt bar and when the control nut 51 is at the other end of the tilt bar the valves that were open are closed and the valves that were closed are open.

Of the pair of valves 99 and 9 I, one of the valves is connected by a suitable conduit to booster cylinder 89 and the other valve is connected by a suitable conduit to booster valve 8|, as hereinbefore set out, and of the pair of valves 92 and 93, one is connected by a suitable conduit to booster cylinder 89 and the other valve is connected to a suitable conduit to booster cylinder 8|, as hereinbefore set out.

The main control valves 95 and 96 located on 6 control housing 39 are connected by conduits 99h, 9|b, 92h and 9312 to the stations or valves 99, 9|, 92 and 93, so that each of the main control valves and 96 is adapted to connect one pair of the control valves or stations 99 and 9| or 92 and 93 to a source of vacuum, that is, the manifold 29 in the particular construction shown.

The arrangement, briefly, is this: Control valves 95 and 96 are connected to a source of vacuum and these main control valves are adapted to be opened and closed, depending upon the direction of misalignment of the vehicles, and each of the main control valves is connected to one pair of the control valves 99, 9|, 92 and 93 and of a pair of control Valves one is connected to one booster cylinder and the other is connected to the other booster cylinder, and of a pair of the control valves 99, 9|, 92 and 93, one is open and the other is closed, depending on whether control nut 51 is at one end of lead screw 55 or the other end of lead screw 55.

Fig. 7 is a sectional view of the main control valve 99 having conduits |95 and |95 connected thereto. Main control valve 95 has conduits |93 and |94 connected thereto. Each of the main control valves 95 and 96 has a piston |98 and there is a compression spring |99 bearing against the piston |98 to urge the piston into open position. Each of the main control valves 95 and 96 also has a piston rod ||9 connected thereto, said piston rod being adapted to be reciprocated or moved back and forth depending on the direction of misalignment of the Vehicles I5 and I6. In the main control valve 96 shown in Fig. 7, the conduit |95 leads to the source of vacuum and the conduit |96 leads to one pair of the control valves, the passageways ||2 being opened and closed by piston |98. The aperture ||3 which is provided in each of the main control valves 95 and 96 serves to break the vacuum within the supply conduit |99 whenever the piston |98 is moved to shut oil? the supply vacuum through |95 so that no vacuum will exist in the supply line |96. A suitable air filter ||4 is provided on each of the main control valves 95 and 95 so that no foreign substance can enter into the Vacuum supply lines.

Auxiliary pistons H1 and ||8 (see Fig. 5) are provided Within control housing 39 and these auxiliary pistons are rigidly connected through slots |29 in control housing 39 to arms |2| and |22, respectively, which arms are in turn rigidly connected to semi-circular members |24 and |25, said semi-circular members having xedly mounted thereon push arms |21 and |28, respectively. The semi-circular members are rigidly connected together by rods |26. Push arms |21 and |28 may be initially adjusted so that main control valves 95 and 96 will be correctly controlled, by means of nuts and bolts |3| which are best shown in Fig. 5, the bolt fitting within a slot provided within push arms |21 and |28. The push arms |21 and |28 are connected by tension springs |33 to control housing 39 shown in Fig. 5 so that the springs serve to put the push arms in a central or neutral position, the springs 39 and 49 urging auxiliary pistons ||1 and ||9 in one direction and springs |33 urging auxiliary pistons ||1 and ||8 in the opposite direction .so that whenever the auxiliary pistons and push arms are moved from their neutral position they will be urged to return to their neutral position.

Push arms |21 and |28 have levers |31 and |38, respectively, pivoted thereon which levers are in turn pivoted on arms |49 and 14|, said 7 last named arms being pivoted on piston rods III) of the main control valves 95 and 96. The arms |40 and |4| are pivoted on supports |43 which supports are rigidly connected to control housing 39. It will be seen, then, that when push arms |21 and |28 are moved, the pistons |98 within rnain control valves 95 and 9S will be moved and, therefore, the main control valves 95 and 96 will be open and closed, depending upon the direction and magnitude of the push arms |21 and |28.

Whenever the vehicles I5 and I3 are misaligned the springs 39 and 49 within one end of housing 30 will be compressed thereby forcing the auxiliary cylinder against which it bears to move thereby moving the push arm connected to the auxiliary cylinder, thereby opening one of the ymain'control valves 95 and 9S and serving to close the other main control valve because the auxiliary cylinders are connected together by rods |26. The main control valves 9:5 and 95 are set up So that when the vehicles are aligned the main control valves are open and, therefore, the conduits leading from the main control valves to the control stations or valves are connected to the supply of vacuum, but when the vehicles are misaligned in one direction, one of the main control valves is opened and the other control valve is closed and when the vehicles are misaligned in the other direction the main control valve that was closed is opened and the main control valve that was open is closed so that, depending on vthe direction of misalignment, one pair of con;- trol stations or valves is connected to a source of vacuum whenever the vehicles are misaligned, and all the control stations connected to a source of vacuum when the vehicles are aligned, one booster means opposing the other booster means to serve to keep the turnable wheels of the towed vehicle I6 aligned.

The levers |31 and |39 are slidably supported on supports |43 by means of pins |95 which fit within levers |31 and |39 and rit within slots provided in support |43, which can best be seen in Fig. 5 in the case of lever |31, the dot-dash lines showing the slot provided in support |133. This construction allows levers |31 and |38 to move arms |49 and |4| while maintaining the ends of the levers closest to push arms |21 and |28 in alignment with the line of travel of push arms |21 and |28.

The operation ci' the booster means is substantially as follows: In Fig. 1 it can be Seen that when the vehicles are misaligned as shown, that is, when the vehicles are moving forwardly and to the right, the main control valve 96 will be open because the springs 39 and 49 within the left hand end of housing 39 will be compressed, thereby pushing auxiliary piston H8 to the left as the piston is shown in Fig. 5, and since the auxiliary pistons H1 and ||8 are connected to one another by means or rods |25, auxiliary pis'- ton I1 will be moved toward the left and therefore push arm |21 will be moved toward the left, moving lever |31 to the left, pulling piston rod I I of main control valve 99 to the right, thereby moving piston |98 of main control valve 99 to the right, thereby connecting conduits |95 and |96, see Figs. and 1. Main control valve 93 being connected to one pair of control stations or valves 92 and 83 and control station or valve 92 being connected to booster cylinder 89, will connect booster cylinder 80 to the intake mani- -fol'd thereby drawing piston rod 85 to the left, as

the device is depicted in Fig. 1, thereby assisting in tilting turnable wheels 21 as shown in Fig. 1.

While the booster means is performing the above operations the springs 39 and 40 within the left hand end of housing 39 are urging .piston 33 to remain in its central position, as the parts are depicted in Fig. 1, pivoting the main tilt lever 36 so as to tilt tilt bar 43 in a counter-clockwise direction, as the tilt b'ar is depicted in Fig. l., so that the main tilt lever `and the booster means together turn the turnable wheels 21.

When describing the main control valves 95 and 9S conduit |96, in the case of main control Valve 96, was said to lead to one pair of control valves or stations and, in the cas'e of main con'- trol valve 95, `conduit |94 would lead to one pair of lthe control valves or stations. Also, conduits b. 9Ib, 92o land 93D were said to lead from main control valves and 96 to control valves or stations 90, 9|., 92 and 93'. Actually it is lnot particularly important how the main control valves 95 and 96 are connected to control valves or stations 90, 9|, 92 and 93. It may be that in some cases it is desirable for one conduit, say conduit |96, to lead from main control valve 96 all the way back to its pair of control valves or stations 92 and 93 where the conduit can be bifurcated into conduits 92h and 93h. On the other hand, it may be desirable to have conduit |95 bifurcated soon after it leaves main control valve 96 so that conduits 92h and 93h are proe vided adjacent main control valve 96 and lead all the way back to control valves or stations 92 and 93. In any event, conduit |96 at some point branches oi into conduits 92h and 93o and cone duit |34 for main control valve 95 branches olf into conduits 99o and SIb.

If the vehicles are moving forward and the towing vehicle |5 moves to the left, the arrangement of the parts will be as shown in Fig. 2 and since the vehicles are still moving forward, as they were in Fig. l, the control nut 51 will still .be at the upper end of the tilt bar 43 as the device is depicted in Fig. 2, and so upon misalignment of the vehicles which will be in the opposite direction from that depicted in Fig. 1, the turnable wheels 21 of the towed vehicle I6 will be turned in the opposite direction. Upon this misalignment of the vehicles I5 and I6 in the opposite direction the reverse action on valves 95 and 98 is effected, namely, that main control valve 95 is opened and main control valve 96 is closed. Since main control valve 95 is connected by conduits |04, 99h and 9Ib to control stations or valves 90 and 9|, -whichever of these control valves or sta'- tions is open the booster cylinder connected thereto will be connected to a source of vacuum. As can be seen from Fig. 12 wherein the control nut 51 is at the upper end of the lead screw, control valve or station 9| is open and since this control valve or station is connected to booster cylinder 8|, booster cylinder 8| will be connected to the source of vacuum and therefore the piston rod 86 will be moved toward the right of the drawing as the device is depicted vin Fig. 2.

When the vehicles are moving backward and to the left, the partsv will be in the position shown in Fig. 3. At the time that the gear shift 22 on the towing vehicle I5 is thrown into reverse, that is, so as to contact contacts 60, the electric motor 53 will be energized so as to cause the control nut 51 to move to the opposite end of the tilt bar 43 from the position shown in Fig. 2, to the position shown in Fig. 3. Therefore, the vehicles in Fig. 3 will be misallgned in the saine direction as shown in Figi, Vbut because the control nut has been reversed the turnable wheels 21 of the towed vehicle I6 will be turned in the opposite direction from that disclosed in Fig. 1 which is the desired direction since they will, in effect, track the turnable wheels 25 of the towing vehicle. It will be appreciated that actually it would seem, in Fig. 3, since the vehicle is moving backward, that the turnable wheels 25 on the towing vehicle l5 are tracking the turnable wheels 21 on the towed vehicle, but since it is the turnable wheels, 25, or, more correctly, the misalignment of the vehicles which results in the turning of the `turnable wheels 21, it is not deemed improper to say that the turnable wheels 21 are tracking the turnable wheels 25.

In Figg, the main control valve 96 will be open connecting control station or valve 93 to a source or vacuum and since control station `93 will be open as can be seen in Fig. 3, and since control station or valve 93 is connected to booster cylinder 8|, the piston rod 86 of booster cylinder 8| will be drawn toward the right, as the parts are depicted in Fig. 3, thereby assisting in turning the turnable wheels 21.

When the vehicles are moving backward to the right the parts will be in the position shown in Fig. 4, in which the main tilt lever 36 will function in the reverse manner as it functioned in Fig. 3, thereby turningthe turnable wheels 21 in the reverse direction from that depicted in Fig. 3. `The main control valve 95 will be open and since it is connected to control station or valve 9i) which, in turn, is connected to booster cylinder 83, booster cylinder 80 will be connected to a source of vacuum, and therefore piston rod 85 will be drawn toward the left tilting tilt bar 43.and assisting the main tilt lever 36 in turning the 4turnable wheels 21 on the towed vehicle.

In Figs. l, 2, 3 and 4, the push arms |21 and |28 are shown in some instances in slanted position. They are shown this way to indicate that the slanted push arm is the one which is pushing whereas the unslanted push arm is the one doing the pulling. Actually there -is no slanting or deflection -of the push arms |21 and |28 since they are rigidly connected to the semi-circular members |24 and |25.

Means are provided on the towing vehicle |6 to bring the tilt bar 43 back to a neutral position and these means are best shown in Figs. 1, 9 and 1l, and these means comprise a spring-strip member |53 which has knobs |5| on the ends thereof tting within sockets |52, said sockets being pivoted at I 54 to the towed vehicle I6. A tension spring |55 is connected to both of the socket members so as to urge the socket members toward one another. Chains |51 connect socket members |52 and standards |50 and prevent the socket members |52 from moving any further in toward each other than they are shown in Fig. 11. However, one of the socket members may move toward lits standard against the resistance of tension spring |55.

The operation of this centering means ls as follows: The push lever 41, as shown in Figs. 9 and 1l, is moved when the tilt bar 43 is tilted and will slide along spring-strip member |50 somewhat deforming the spring-strip member and the socket member |52 will be moved toward its standard against the resistance of tension spring |56 and also against the resistance of strip member |53, and when the force on the tilt bar 43 is released the spring-strip member and the tension spring |56 will serve to strongly 10 urge the push lever 41 back to its central position so that the turnable wheels 21 on the towed vehicle will be automatically aligned by this centering means.

It is desired that when the vehicles are moving backward the apparatus for turning the turnable wheels 21 on the towed vehicle be more sensitive in turning the turnable wheels 21 than when the vehicles are moving forward, and this is accomplished by pivoting tilt bar 43 somewhat off center, this being most obvious from Fig. 9 where,- in it can be seen that the pivot 46 is definitely 01T center from the opposite ends of the lead screw. Also see Fig. 3 where the control nut is at .the lower end of the lead screw as the device is depicted there and wherein the off center pivoting of the tilt bar is obvious. It will be appreciated, then, that when the control nut is inthe position shown in Fig. l there will be a longer leverage between the lever ,42 and the pivot`46 of the tilt bar than when the control nut' 51 is in the position shown in Fig. 3 and, therefore. with the longer the lever the less sensitive for the same amount of movement will be the turnable wheels 21 and therefore the apparatus-is more sensitive when the vehicle is movingV backward than forward.

Each of the booster cylinders 39 and 8| has passageways |63 leading to the atmosphere, on the sides of the pistons opposite the conduit entrance side of the piston so that when air-is within either of the conduits leading from-the main control valves and 96, the piston Within the booster cylinder which is connected to the conduit which has air therein will be in a balanced position. f

The booster means 30 and 8| will aid the centering means in centering the turnablevwheels of the towed vehicle l5 when the vehicles are aligned as before explained since both main control valves 95 and 96 will be open and therefore, one booster cylinder will be opposing the other booster cylinder, and since they willV pullgan equal amount there will be a balanced condition.

Although the cylinder 30 is shown mounted' on the towing vehicle and the piston connectedto means which are swingably mounted on the towed vehicle, it is obvious that the cylinder could be mounted on the towed vehicle and the piston connected to the towing vehicle, this being a mere reversal of the parts and in such case the cylinder would, of course, be connected to the main tilt lever.

Various changes may be made in the details 'of construction without departing from 'the spirit and scope of the invention as dened by th 'appended claims.

I claim:

l. In combination with a towing vehicle having turnable wheels and a towed vehicle having turnable wheels, means responsive to misalignment of the vehicles for turning the turnable wheels of the towed vehicle in the directionA opposite to the direction in which the turnable wheels of the towing vehicle are turned,`the turnable Wheels oi the towing Vehicle causing misalignment of the vehicles when turned while the vehicles are moving, control means providing two pairs of energy-transmitting stations, means assisting the first-named means in turning the turnable wheels of the towed vehicle for urging the turnable wheels of the towed vehicle in one direction when receiving energy 'from either of two of the stations and for urging the turnable wheels of the towed vehicle in the other direction when receiving energy from either of the remaining two stations, said two of the stations consisting of one station from each of the pairs of stations, means connecting the assisting means and the stations to transmit energy to the assisting means whenever the station is eiTective to transmit energy and is provided with energy, means operable at the time the vehicles move `forward for causing one station of each pair to become ineffective to transmit energy and the other station of each pair to be effective to transmit energy and when the vehicles move backward for causing the stations that were ineffective to become effective and the stations that were effective to become ineffective, and means operable when the towing vehicle turns in one direction for providing energy to said one pair of stations and when the towing vehicle turns in the other direction for providing energy to said other pair of stations.

2. In combination with a towing 'vehicle and a towed vehicle having turnable wheels 'means swingable mounted on the towed vehicle and connected to the turnable wheels so as to turn the turnable wheels when swung, means connecting the vehicles responsive to misalignment of the vehicles for urging the rst-named means to swing in one direction when the vehicles are misaligned one way and to swing in the other direction when the vehicles are misaligned the opposite way, means for reversingr the direction in which 'the second named means causes the first-named means to swing when the vehicles re- 'verse direction of movement from forward to backward or vice versa, control means providing two pairs of energy-transmitting stations, means assisting the rst-named means in turning the turnable wheels of the towed vehicle for urging the turnable wheel-s in one direction when receiving energy from either of two of the stations and for urging the turnable wheels in the other direction when receiving energy from either of the remaining two stations, said two of the stations consisting of one station `from each or the 'pair of Stations, and means connecting the assisting means and the stations to transmit energy Vto the assisting means whenever a station is effective to transmit energyand is provided with energs', the third-named means being operable at the time the vehicle is moved forward for causing one station of each pair lto become ineffective to transmit energy and theother station of each pair to become effective to transmit energy and when the vehicle is moved backward for causing therstations that were ineffective to become effective and the stations that were veffective to become ineiective, he second-named means being operable when the towing vehicle turns in one direction for providing energy to said one pair of stations and when the towing vehicle turns in the other direction for providing energy to said other pair of stations.

3. In combination with a towed vehicle having turnable wheels and a towing vehicle, means oscillatably mounted on the towed vehicle and connected to the turnable wheels to turn the turnable wheels when tilted, means connecting the .first-named means and the towing vehicle responsive to misalignment of the vehicles for urging the first-named means to tilt in one direction when the vehicles are misaligned in one way and to tilt in the other direction when the vehicles are misaligned the opposite way, means for reversing the direction in which the second-named means causes the first-named means to tilt when 'the vehicles reverse direction of movement from forward to backward or vice versa, booster means for assisting turning of the unable wheels, means providing conduits between a source of vacuum and the booster means, the booster means being actuatable when connected to the source of vacuum, control means providing two pairs of valves in the conduits between the source ci vacuum and the booster means, the booster means urging the turnable wheels in one ldirection when connected to the source of vacuum through two of the valves and for urging the turnable wheels in the other `direction when connected to the source of vacuum through the remaining two valves, said two of the valves consisting of one valve from each of the pair of valves, the third-named means being operable at the time the vehicles move forward for causing one valve of each pair to .close and the other valve of each pair to open and when the vehicles move backward for causing the valves that were open to close and the valves that were rclosed to open, means associated with the conduits between the source of vacuum and the pair of valves to open and close these conduits, the second-named means controlling the last-named means so that when the towing vehicle turns in one direction the conduit to one pair of valves is yopen and the conduit to the other pair closed and when the towing vehicle turns in the other direction the conduit to the other pair of valves and the conduit to said one pair of valves is closed.

4. In combination with a towed vehicle having turnable wheels and a towing vehicle, means oscillatably mounted on the towed vehicle and connected to the turnable wheels actuatable to turn the .turnable wheels when tilted, means connecting the iirst-named means and the towing 'vehicle responsive to misalignment of the vehicles for urging the rst-named means to tilt in one direction when the vehicles are misaligned one way and to tilt in the other direcion when the vehicles are misaligned the opposits way, means for reversing the direction in which the second-named means causes the firstnamed means to tilt when the vehicles reverse direction of movement from forward to backward or vice versa, control means providing two pairs of valves, means connecting one pair oi valves to a source of vacuum, the last-named means being adapted to be Iopened and closed to cut yoff the valves from the source of vacuum or connect the valves to the source of vacuum. means connecting the other pair of valves to a source of vacuum, the last-named means adapted to be opened and closed to cut 0E said other pair of valves from the source of vacuum or connect said other pair of valves to the source oi vacuum, booster means for assisting the firstnamed means in turning the turnable wheels for urging the turnable wheels in one direction when connected to a source of vacuum through either of two of the valves and for urging the turnable wheels in the other direction when connected to a source cf vacuum through either of the remaining two valves, said two of the valves consisting of one valve from each 0i the pair of valves, and means providing separate connections between the valves and the booster means so that when any of the valves are open and connected to a source of vacuum, the booster means will be lconnected to a source or vacuum, the third-named means being operable at the time the vvehicles move forward for causing one vehicle moves the other way and to open both the.

fth and sixth-named means when the vehicles are aligned.

5. An apparatus adapted to be applied to a towed vehicle having turnable wheels and a towing vehicle for causing the turnable wheels to turn when the vehicles are misaligned, com-x prising means adapted to be oscillatably mounted on the towed vehicle and connected to the turnable wheels to turn the turnable wheels when tilted, means connected to the rst-named means Y and adapted to be connected to the towing vehicle responsive to misalignment of the vehicle for causing the rst-named means to tilt in one direction when the vehicles are misaligned one way and to tilt in the other direction when the vehicles are misaligned the opposite way, means for reversing the direction in which the second-named means causes the firstnamed means to tilt when the vehicles reverse direction of movement from forward to backward or vice versa, booster means for assisting turning of the turnable wheels, means providing conduits between a source of vacuum and the booster means, the booster means being actuatable when connected to the source of vacuum, control means providing two pairs of valves in the conduits between the source of vacuum and the booster means, the booster means urging the turnable wheels in one direction when connected .to the source of vacuum through two of the valves and for urging the turnable wheels in the opposite direction when connected to the source of vacuum through the remaining two valves, said two of the valves consisting of one valve for each of the pair of valves, the thirdnamed means being operable at the time the vehicles move forward for causing one valve of each pair to close and the other valve of each pair to open and when the vehicles move backward for causing the valves that were open to close and the valves that were closed to open, and means associated with the conduits between the source of vacuum and the pairs of valves to open and close these conduits, the second-named means controlling the last-named means so that when the towing vehicle turns in one direction the conduit to one pair of valves is open and the conduit to the other pair oi valves is closed and when the towing vehicle turns in the other direction the conduit to said other pair of valves is open and the conduit to said one pair of valves is closed.

6. In combination with a towed vehicle having turnable wheels and a towing vehicle, means on the towing vehicle providing a cylinder mounted off center of the towing vehicle, means on the towed vehicle providing a piston slidable within the cylinder, means connecting the piston and the turnable wheels for urging the turnable wheels to turn when the piston moves relative to the towed vehicle, spring means within the cylinder arranged to act on the piston for urging the piston to remain in a predetermined position relative to the cylinder, the spring means being stressed when the vehicles are misaligned, at

least one auxiliary piston within the cylinder and movable when the spring means is stressed, booster means connected to the third-named means to aid the third-named means in turning the turnable wheels, means for connecting the booster means to a supply of vacuum to actuate the booster means, means controlled by the auxiliary piston for opening and closing thevconnection from the source of vacuum to the booster means, means between the last-named means and the booster means for opening and closing the connection be tween the source of vacuum and the booster means, and means for reversing the direction in which the third-named means urges the turnable wheels to turn whenever the vehicles reverse movement from forward to backward or backward to forward, the reversing means acting to control the means between said last-named means and the booster means so that the booster means is actuated to always aid the third-named means in turning the turnable wheels.

7, In combination with a towed vehicle having turnable wheels and a towing vehicle, means on one of the vehicles providing a cylinder mounted on said one of the vehicles oi center thereof, means on the other vehicle providing a piston slidable within the cylinder, means connecting the means on the towed vehicle and the turnable wheels for urging the turnable wheels to turn when said means on the towed vehicle moves relative to the towed vehicle, means urging the turnable wheels to remain in aligned position, the piston and the cylinder being urged by the fourthnamed means to move relative to one another when the vehicles are misaligned, spring means operatively associated with the cylinder and the piston urging the piston to remain in a predetermined position relative to the cylinder so that when the vehicles are misaligned the spring means urges the turnable wheels to turn against the resistance of the fourth-named means, and means for reversing the direction in which the third-named means urges the turnable wheels to turn whenever the vehicles reverse movement from forward to backward or backward to forward.

8. An apparatus adapted to be applied to a towed vehicle having turnable wheels and a towing vehicle for causing the turnable wheels to turn when the vehicles are misaligned, comprising means adapted to be mounted on the towing vehicle providing a cylinder whose axis is off center of the axis of the towing Vehicle, means adapted to be mounted on the towed vehicle providing a piston slidable within the cylinder, means connected to the piston and adapted to be connected to the turnable wheels for urging the turnable wheels to turn when the piston moves relative to the towed vehicle, means adapted to be connected to the turnable wheels to urge the turnable wheels to remain in aligned position, the piston being urged by the fourth-named means to move relatively to the cylinder and remain in a fixed position relative to the towed vehicle when the vehicles are misaligned, spring means operatively associated with the cylinder and the piston urging the piston to remain in a predetermined position relative to the cylinder so that when the vehicles are misaligned the spring means urges the turnable wheels to turn against the resistance of the fourth-named means, and means for reversing the direction in which the third-named means urges the turnable wheels to turn whenever the vehicles reverse emanare imovement from :iorward to baclz'wani or .backward 1to 'forward.

49. .In combination 'with a towing :vehicle tand .a towed 4vehicle :having .steerable wheels, :a lead :screw rsupported 'by the towedA vehicle for rbodily `pivotalmovement about'agpoint intermediate ,the lends of .theilead screw .and for axial rotation, :the leadscrewbeing'connected Yto Ithe .steeringwheels auf lthe Atowed vehicle for turning the steering wheels of 'the'towed vehicle whenthe lead screw -is :bodily turned-a nutnon the leadscrew adapted 'on'axial rotation ofthe .lead screw .to be moved .fromone side ofthe ypivot point -of theY lead screw .rto' the other,. means `connected to .the fnutqand :operable by vmisalignment Vof the vehicles to vurge .lead :screw .to bodily turn, means operable .by

shifting .of Vthe vehicles from :forward .to reverse lor -vicefversacfoncausing a .ch angeover of thelnut irom-.onesideof'thepivot point of .the leadgscrew tothe othenand booster Vmeans:operatively c onnected to the lead screw -for urging Ythe lead sscrewlto bodily turn and `being operatively connected `to 4the rst-,named means .and the nut .to 'be .controlled therebyso that the .booster means operates toalways urge the leadscrew tobodily .turnin .the same direction which the first-named `means urges vthe lead screw to .bodily turn.

10. In combination .with a towing vehicle and .a .towed vehicle .having .steerable wheels, 4a lead .screw supported `by vthe towed vehiclefor bodily .pivotal movement abouta pointintermediate the ends of the lead .screw ,and for .axial rotation, the lead screw being connected to .the steering .wheels of ,the 'towed vehicle for turning the steering wheels `of ythe towed vehicle when 'the'lead 1 y.screw is bodily turned, a nut on thelead screw adapted on axialrotation of the leadscrewto be )moved from `one `side or" .the pivot point of the lead screw to theother, means connected tothe .nut and operable bymisalignmentof the vvehicles .to urge leadscrew to bodily turn, and meansfor causing a changeover' of Vthenut from one side of the pivot point of the lead screw to the other.

'11. In combination with a'towing vehicle -and 'a Atowed vehicle having steerable wheels, a lead screw supported by the towed vehicle-'for bodily pivotal movement about a point intermediate the ends of the lead screw and for axial rotation, the lead screw being connected to the steering wheels'of the towed vehicle for turning the steering wheels of the towed vehicle `when the lead screw is bodily turned, va nut on the lead screw adapted on raxial rotationof the lead screw :to V.be moved 'from one side of the pivot vpoint `of the 'leadscrew to the otherpmeansconnectedtothe nut and operablelby misalignment ofthe vehicles '-to Yurge lead screw to bodily turn, .and :means voperable 'by shifting Vof vthe vehicles `from forward to reverse or vice versa for causing a changeover of the nut `from one side of the .pivot :point of the lead screw .to the other.

12. In combination with atowing vehicleand la :towed vehicle having steerable wheels, la llead :screw supported by the ztowed yvehicle for .bodily .pivotal movement :about a 'point intermediate theendsv of the lead screw and for axial rotation, nthe lead `screw being connected to the steering :wheelsof rthe towed vehicle for turning 'the steer- -ing wheels of the towed vehicle when-the lead screw :is bodily turned, a nut on the lead screw v adapted on yaxial rotation of :the leadscrew ,to .be zmoved :from one Yside of Athe `pivot ypoint of .the lead :screw to the other, means connected to the nut `and operable by misalignment of 'the vehicles `:to v.urge lead screw to bodily turn, means for causing `ra changeover lof the .nut from one :side

of the pivot polntof'the leadscrew tothe other, iand booster means 'operatively connected ltothe lead screw for urging the lead screw to bodily turn in thesame direction whichrthe rst-named .means urges the lead screw yto bodily turn.

13. .Incombination with a towing vehicle and a towed vehicle having steerable wheels, a lead screw supported by the towed vehicle for bodily pivotal movement about a point lintermediate the ,ends-of the lead screw and foraxial rotation. the lead screw being connected to the steering wheelsof the towed vehicle for turning thesteering wheels of the towed vehicle when the 4lead -sorew is bodily turned, a nutvon the vlead screw adaptedon axial rotation of the leadfscrew to be moved fromone side ofthepivotpoint ofthe lead .screw .to the Othenmeans connected to the nut and operable by Amisalignment of the vehicles to urge lead :screw to bodily turn, vmeans :for causing achangeover .of the nut from one iside of thegp-ivot-point of the lead screw to the other,

'and booster means operatively connected to the lead screw for urging the lead screw to bodily turnandbeing operatively connected to the iirstnamed means and the nut to be controlled thereby sothat the boostervmeans operates to always urge the lead screw to bodily turn in the same direction which the rst-named means urges the lead'screw'to turn.

A14. In combination with a towing vehicle and a towed vehicle having steerable wheels, va tilt bar supported bythe towed 'vehicle for bodily pivotal movement about a point `intermediate the ends of the tilt barand being connected=to the steering wheels of the towed vehicle for vturning the steering wheels of' the towed vehicle when the tilt barvis tilted, means Vconnected to the'tilt bar and operable by misalignment of the vehicles for urging the tilt bar to bodily turn, said means being movable with ,respect to the tilt bar lfrom one side of the tilt bar to the other side to cross over the'pivot point thereof, Ameans operable by shifting of the vehicles from forward to reverse or vice versa for causing a changeover of the first-named means from -one side of the tilt bar to the other, and booster means operatively `con nected to the tilt bar for urging the tilt bar to bodily turn and being operatively connected to the iirst-named means and to the changeovercausing means to be controlled so that the booster means operates to always urge the tilt bar to bodily turn in `the 'same direction ,in which .the

rst-namedmeans urges Athe tilt bar-,to bodily vbar and operable bymisalignment Vof thevehicles for urging the tilt bar to vbodily-turn, lsaid means -being movable with respect to the vtilt bar from one sideof the tilt bar to the-other side to cross over 4the pivot point thereof, and means-operable by shifting of the vehicles from forward to reverse or vice versa for causing a vchangeover'oi? the rst-namedmeans from one side of the tilt :bar `to 'the other.

.16. In combination with a ytowing vehicle and a towed vehicle having steerable wheels, a tilt bar supported lby the ,towed vehicle Vfor bodily pivotal movement about a point intermediate the ends of the tilt bar and being connected to the steering wheels of the towed vehicle for turning the steering wheels of the towed vehicle when the tilt bar is tilted, means connected to the tilt bar and operable by misalignment of the vehicles for urging the tilt bar to bodily turn, said means being movable with respect to the tilt bar from one side of the tilt bar to the other side to cross over the pivot point thereof, means for causing a changeover of the first-named means from one side of the tilt bar to the other, and booster means operatively connected to the tilt bar for urging the tilt bar to bodily turn in the same direction in which the first-named meansurges the tilt bar to bodily turn.

17. In combination with a towing vehicle and a towed vehicle having steerable wheels,=a tilt bar supported by the towed vehicle for bodily pivotal movement about a point intermediate the ends of the tilt bar and being connected to the steering wheels of the towed vehicle for turning the steering wheels of the towed vehicle when the tilt bar is tilted, means connected to the tilt bar and operable by misalignment of the vehicles for urging the tilt bar to bodily turn, said means being movable with respect to the tilt bar from one side of the tilt bar to the other side to cross over the pivot point thereof, means for causing a changeover of the first-named means from one side of the tilt bar to the other, and booster means operatively connected to the tilt .bar for urging the tilt bar to bodily turn and being operatively connected to the firstnamed means and to the changeover-causing means to be controlled thereby so that the booster means operates to always urge the tilt bar to bodily turn in the same direction in which the first-named means urges the tilt bar to bodily turn.

18. In combination with a towing vehicle and a towed vehicle having steerable wheels, a tilt bar supported by the towed vehicle for bodily pivotal movement about a point intermediate the ends of the tilt bar and being connected to the steering Wheels of the towed vehicle for turning the steering wheels of the towed vehicle when the tilt bar is tilted, means including a swingably mounted tilt bar actuating member operatively connected to the tilt bar operable by misalignment of the vehicles for urging the tilt bar tozbo'dily turn, said tilt bar actuating member being swingable from one position where it is connected to the tilt bar adjacent one end of the tilt bar to another position wherein it is connected to the tilt bar adjacent the other end of the tiltbar, means operable by shifting of the vehicles from forward to reverse or vice versa for causing a, changeover of the tilt bar actuating member from one end of the tilt bar to the other, and booster means operatively connected to the tilt bar for urging the tilt bar to bodily turn and being operatively connected to the first-named means and the second-named means to be controlled thereby so that the booster means operates to always urge the tilt bar to bodily turn in the same direction which the first-named means urges the tilt bar to bodily turn.

19. An apparatus of the class described. a towing vehicle having steerable wheels and a towed vehicle having steerable wheels, means operable for turning the steerable wheels of the towed vehicle in the opposite direction from the direction in which the steerable wheels of the towing vehicle are turned, control means for thevflrst-named means providing four stations each capable of causing actuation of therstnamed means, two of the stations being capable of -causing actuation of the first-named means in a manner such as to urge the steerable wheels of the towed vehicle to turn in one direction and the remaining two of the stations being capable of causing actuation of the first-named means in a manner such as to` urge the steerable wheels of the towed vehicle to turn -in the opposite direction, means operable by misalignment of the vehicles in one direction for causing said two of the stations to be ineffective to cause actuation of the first-named means and operable by misalignment of the vehicles in the opposite direction for causing said remaining two of the stations to be eective to cause actuation of the first-named means, and means operable by shifting of the vehicles from forward to reverse for causing one station of said two of the stations and one station of the said remaining two of the stations to be ineffective to cause actuation of the first-named means and operable by shifting of the vehicles from reverse to forward for causing the other of said two of the stations and the other station of said remaining two of the stations to be ineffective to cause actuation of the first-named means.

20. A device of the class described adapted to be attached to a towed vehicle having steerable wheels and a towing vehicle comprising a lead screw, means attachable to the towed vehicle and supporting the lead screw for bodily pivotal movement about a point intermediate the ends of the lead screw and for axial rotation, means for connecting the lead screw to the steerable wheels of the towed vehicle to enable the lead screw to cause turning of the steerable wheels of the towed vehicle when the lead screw is turned, a nut on the lead screw adapted on axial rotation of the lead screw to be moved from one side of the pivot point of the lead screw to the other, means attachable to the vehicles and operable by misalignment of the vehicles to urge the lead screw to bodily turn, and means attachable to the vehicles and operable by shifting of the vehicles from forward to reverse or vice versa for causing a changeover of the nut from one side of the pivot point of the lead screw to the other.

21. A device of the class described adapted to be attached to a towed vehicle having steerable wheels and a towing vehicle comprising a lead screw, means attachable to the towed vehicle and supporting the lead screw for bodily pivotal movement about a point intermediate the ends of the lead screw and for axial rotation.

means for connecting the lead screw to the steerable wheels of the towed vehicle to enable the lead screw to cause turning of the steerable wheels of the towed vehicle when the lead screw is turned, a nut on the lead screw adapted on axial rotation of the lead screw tolbe moved from one side of the pivot point of the lead screw to the other, means attachable to the vehicles and operable by misalignment of the vehicles to urge the lead screw to bodily turn, means attachable to the vehicles and operable by shifting of the vehicles from forward to reverse or vice versa for causing a changeover of the nut from one side of the pivot point of the lead screw to the end, and booster means operatively connected to the lead screw for urging the lead screw 'to bodily turn in the same direction in which the rst-named means urges the lead screw to bodily turn. Y

22. A device of the class described adapted to be attached to a towed vehicle having steerable wheels and a towing vehicle comprising a lead screw, means attachable to the towed vehicle and supporting the lead screw for bodily pivotal movement about a point intermediate the ends of the lead screw and for axial rotation, means for connecting the lead screw to the steerable wheels of the towed vehicle to enable the lead screw to cause turning of the steerable wheels of the towed vehicle when the lead screw is turned, a nut on the lead screw adapted on axial rotation of the lead screw to be moved from one side of the pivot point of the lead screw to the other, means attachable to the vehicles and operable by misalignment of the vehiclesv to urge the lead screw to bodily turn, means attachable vehicles from forward to reverse or vice versa for REFERENCES CITED The following references are of record in the le of this patent:

UNITED vSTATES PATENTS Number Name Date 1,245,054 `Spencer Oct'. 30, 1917 1,849,260 Williams Mar. 15, 1932 2,018,197 Vorech et al Oct. 22, 1935 

